Macrolide antibiotics of the formula (I) according to the present invention are described in, for example, Helvetica Chemica Acta 38, 1445-1448 (1955), id. 45, 129-138 and 620-630 (1962), Journal of Antibiotics 23, 105-106 (1970), id. 24, 347-352 (1971), etc., and the process for preparing these antibiotics and their physicochemical properties are already known. Further, it is known that these compounds are effective in extermination of vermin such as acarids and cockroaches (see the specification of Japanese Patent Publication No. 46-28100), and it is also known that said macrolide antibiotics are useful as medicines for domestic animals and fowls, more specifically as growth promoting agents for animals (see the specification of Japanese Patent Public Disclosure No. 54-40178) and anti-coccidiosis agents (see the specification of Japanese Patent Public Disclosure No. 53-91143).
As immunosuppressive agents, there are known alkylating agents such as cyclophosamide, nucleic acid antimetabolites such as 6-mercaptopurine and azathiopurine, antibiotics such as mitomycin C, steroids, folic acid antagonists such as methotrexate, and plant alkaloids such as colchicine and vinblastine. These immunosuppressive agents are used as agents for suppressing rejection which may occur after transplantation of human organs or as medicines for treating patients suffering from autoimmune diseases. It has recently been noticed that cyclic polypeptides which are typified by cyclosporin A have immunosuppressive activity and noticeably suppress rejection occurring after organ transplantation. At the same time, vigorous studies have been made to achieve application of cyclic polypeptides to autoimmune diseases, and utility of these polypeptides has been confirmed.
The present inventors made exhaustive studies on the activity of compounds of formula (I) on the immune system which have a cyclic structure similar to that of cyclosporins and, as a result, they found the fact that compounds of the formula (I) have immunosuppressive activity. The present invention is based on this finding.